[stable28] feat(database): Primary/replica split

[ChristophWurst]

Manual backports of

• enh: Implement PrimaryReadReplicaConnection #41998
• feat: Track dirty table writes and long transactions #42345
• fix: Avoid using replicas during setup #42504
• fix(db): Fix replica password example config #42890
• fix(db): Do not log transacted reads as dirty read #42929
• feat(db): Make dirty query logging available in production #43185
• fix(db): Execute dirty reads on the primary node #42933
• fix(db): Remove very verbose dirty query logs #42922
• fix(db): Let dirty writes cool off #43297
• fix(db): Unify long transaction log/exception message #43542

Ref #33542

[ChristophWurst]

Tested on a small production instance and this works. The caveat is that it catches lots of queries and logs them as dirty. Most of that happens during cron.php execution because the joblist continuously does a SELECT * FROM oc_jobs … LIMIT 1 mixed with lots of UPDATE oc_jobs … so it looks like there could be dirty reads. Whether there could be any is subject of a research task.